257 lines
8.1 KiB
C
257 lines
8.1 KiB
C
/*
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* Copyright (c) 1999 Peter Wemm <peter@FreeBSD.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/kernel.h>
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#include <sys/ktr.h>
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#include <sys/mutex.h>
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#include <sys/proc.h>
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#include <sys/rtprio.h>
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#include <sys/queue.h>
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/*
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* We have NQS (32) run queues per scheduling class. For the normal
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* class, there are 128 priorities scaled onto these 32 queues. New
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* processes are added to the last entry in each queue, and processes
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* are selected for running by taking them from the head and maintaining
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* a simple FIFO arrangement.
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*
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* Interrupt, real time and idle priority processes have and explicit
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* 0-31 priority which maps directly onto their class queue index.
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* When a queue has something in it, the corresponding bit is set in
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* the queuebits variable, allowing a single read to determine the
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* state of all 32 queues and then a ffs() to find the first busy
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* queue.
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*
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* XXX This needs fixing. First, we only have one idle process, so we
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* hardly need 32 queues for it. Secondly, the number of classes
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* makes things unwieldy. We should be able to merge them into a
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* single 96 or 128 entry queue.
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*/
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struct rq itqueues[NQS]; /* interrupt threads */
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struct rq rtqueues[NQS]; /* real time processes */
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struct rq queues[NQS]; /* time sharing processes */
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struct rq idqueues[NQS]; /* idle process */
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u_int32_t itqueuebits;
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u_int32_t rtqueuebits;
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u_int32_t queuebits;
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u_int32_t idqueuebits;
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/*
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* Initialize the run queues at boot time.
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*/
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static void
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rqinit(void *dummy)
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{
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int i;
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for (i = 0; i < NQS; i++) {
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TAILQ_INIT(&itqueues[i]);
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TAILQ_INIT(&rtqueues[i]);
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TAILQ_INIT(&queues[i]);
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TAILQ_INIT(&idqueues[i]);
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}
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}
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SYSINIT(runqueue, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, rqinit, NULL)
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/*
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* setrunqueue() examines a process priority and class and inserts it on
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* the tail of it's appropriate run queue (based on class and priority).
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* This sets the queue busy bit.
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* The process must be runnable.
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* This must be called at splhigh().
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*/
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void
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setrunqueue(struct proc *p)
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{
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struct rq *q;
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u_int8_t pri;
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mtx_assert(&sched_lock, MA_OWNED);
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KASSERT(p->p_stat == SRUN, ("setrunqueue: proc %p (%s) not SRUN", p, \
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p->p_comm));
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/*
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* Decide which class we want to run. We now have four
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* queues, and this is becoming ugly. We should be able to
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* collapse the first three classes into a single contiguous
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* queue. XXX FIXME.
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*/
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CTR4(KTR_PROC, "setrunqueue: proc %p (pid %d, %s), schedlock %lx",
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p, p->p_pid, p->p_comm, (long)sched_lock.mtx_lock);
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if (p->p_rtprio.type == RTP_PRIO_ITHREAD) { /* interrupt thread */
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pri = p->p_rtprio.prio;
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q = &itqueues[pri];
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itqueuebits |= 1 << pri;
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} else if (p->p_rtprio.type == RTP_PRIO_REALTIME || /* real time */
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p->p_rtprio.type == RTP_PRIO_FIFO) {
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pri = p->p_rtprio.prio;
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q = &rtqueues[pri];
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rtqueuebits |= 1 << pri;
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} else if (p->p_rtprio.type == RTP_PRIO_NORMAL) { /* time sharing */
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pri = p->p_priority >> 2;
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q = &queues[pri];
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queuebits |= 1 << pri;
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} else if (p->p_rtprio.type == RTP_PRIO_IDLE) { /* idle proc */
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pri = p->p_rtprio.prio;
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q = &idqueues[pri];
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idqueuebits |= 1 << pri;
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} else {
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panic("setrunqueue: invalid rtprio type %d", p->p_rtprio.type);
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}
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p->p_rqindex = pri; /* remember the queue index */
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TAILQ_INSERT_TAIL(q, p, p_procq);
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}
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/*
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* remrunqueue() removes a given process from the run queue that it is on,
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* clearing the queue busy bit if it becomes empty.
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* This must be called at splhigh().
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*/
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void
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remrunqueue(struct proc *p)
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{
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struct rq *q;
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u_int32_t *which;
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u_int8_t pri;
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CTR4(KTR_PROC, "remrunqueue: proc %p (pid %d, %s), schedlock %lx",
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p, p->p_pid, p->p_comm, (long)sched_lock.mtx_lock);
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mtx_assert(&sched_lock, MA_OWNED);
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pri = p->p_rqindex;
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if (p->p_rtprio.type == RTP_PRIO_ITHREAD) {
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q = &itqueues[pri];
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which = &itqueuebits;
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} else if (p->p_rtprio.type == RTP_PRIO_REALTIME ||
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p->p_rtprio.type == RTP_PRIO_FIFO) {
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q = &rtqueues[pri];
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which = &rtqueuebits;
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} else if (p->p_rtprio.type == RTP_PRIO_NORMAL) {
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q = &queues[pri];
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which = &queuebits;
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} else if (p->p_rtprio.type == RTP_PRIO_IDLE) {
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q = &idqueues[pri];
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which = &idqueuebits;
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} else {
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panic("remrunqueue: invalid rtprio type");
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}
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TAILQ_REMOVE(q, p, p_procq);
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if (TAILQ_EMPTY(q)) {
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KASSERT((*which & (1 << pri)) != 0,
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("remrunqueue: remove from empty queue"));
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*which &= ~(1 << pri);
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}
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}
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/*
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* procrunnable() returns a boolean true (non-zero) value if there are
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* any runnable processes. This is intended to be called from the idle
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* loop to avoid the more expensive (and destructive) chooseproc().
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*
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* MP SAFE. CALLED WITHOUT THE MP LOCK
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*
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* XXX I doubt this. It's possibly fail-safe, but there's obviously
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* the case here where one of the bits words gets loaded, the
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* processor gets preempted, and by the time it returns from this
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* function, some other processor has picked the runnable process.
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* What am I missing? (grog, 23 July 2000).
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*/
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u_int32_t
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procrunnable(void)
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{
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return (itqueuebits || rtqueuebits || queuebits || idqueuebits);
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}
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/*
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* chooseproc() selects the next process to run. Ideally, cpu_switch()
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* would have determined that there is a process available before calling
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* this, but it is not a requirement. The selected process is removed
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* from it's queue, and the queue busy bit is cleared if it becomes empty.
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* This must be called at splhigh().
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*
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* For SMP, trivial affinity is implemented by locating the first process
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* on the queue that has a matching lastcpu id. Since normal priorities
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* are mapped four priority levels per queue, this may allow the cpu to
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* choose a slightly lower priority process in order to preserve the cpu
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* caches.
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*/
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struct proc *
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chooseproc(void)
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{
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struct proc *p;
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struct rq *q;
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u_int32_t *which;
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u_int32_t pri;
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#ifdef SMP
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u_char id;
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#endif
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mtx_assert(&sched_lock, MA_OWNED);
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if (itqueuebits) {
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pri = ffs(itqueuebits) - 1;
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q = &itqueues[pri];
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which = &itqueuebits;
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} else if (rtqueuebits) {
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pri = ffs(rtqueuebits) - 1;
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q = &rtqueues[pri];
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which = &rtqueuebits;
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} else if (queuebits) {
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pri = ffs(queuebits) - 1;
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q = &queues[pri];
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which = &queuebits;
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} else if (idqueuebits) {
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pri = ffs(idqueuebits) - 1;
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q = &idqueues[pri];
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which = &idqueuebits;
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} else {
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CTR1(KTR_PROC, "chooseproc: idleproc, schedlock %lx",
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(long)sched_lock.mtx_lock);
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return PCPU_GET(idleproc);
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}
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p = TAILQ_FIRST(q);
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#ifdef SMP
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/* wander down the current run queue for this pri level for a match */
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id = PCPU_GET(cpuid);
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while (p->p_lastcpu != id) {
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p = TAILQ_NEXT(p, p_procq);
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if (p == NULL) {
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p = TAILQ_FIRST(q);
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break;
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}
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}
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#endif
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CTR4(KTR_PROC, "chooseproc: proc %p (pid %d, %s), schedlock %lx",
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p, p->p_pid, p->p_comm, (long)sched_lock.mtx_lock);
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KASSERT(p, ("chooseproc: no proc on busy queue"));
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TAILQ_REMOVE(q, p, p_procq);
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if (TAILQ_EMPTY(q))
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*which &= ~(1 << pri);
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return p;
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}
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